The ethanol fermentation potential of C6 sugar hydrolysates were performed using the industrial S. cerevisiae Thermosacc Dry .Three different yeast fermentation approaches were trialled to establish ethanol production and to investigate the effects of biomass degradation compounds generated during pretreatment and those naturally present in CGT. These compounds generally lead to an unfavourable environment for microbial growth resulting in low ethanol titres and productivities, and potentially require removal via an expensive detoxification step (Palmqvist and Hahn- Hägerdal, 2000). In the first two approaches a separate enzymatic hydrolysis followed by fermentation was employed, where fermentation hydrolysates were produced from either recovered washed pretreated fibres (termed WF) or whole pretreated slurries (termed WS). The differences between the two hydrolysates being those from WS contain a complex mixture of sugars and compounds from CGT biomass and degradation reactions. In both approaches glucose was rapidly and completely metabolised by the yeast with the production of high ethanol titres (Table 6).